Positive experience: I dated someone who was already in a primary relationship. They ended it fairly amicably because they felt that my primary relationship was affecting my relationship with them in a way they didn't like.

Positive experience: My monogamous relationship was suffering due to my partner's sudden drop in libido and the tension this caused. Although I had read Polyhacking, we didn't really consider Consensual Non-Monogamy until my partner met another person in an open marriage who framed it as a positive thing. Since we opened up, my partner and I have been much happier, although lately there has been stress due to my partner not currently seeing anyone else and wanting more of my time.

Negative experience: I met someone who was in an open relationship with her husband and a boyfriend. Over the next few months I watched her marriage explode as her husband adjusted poorly to anti-depressants. They are in the process of divorcing, and she is on-again off-again with the boyfriend. My impression is that both she and her husband have emotional issues that may have contributed to this outcome.

Positive experience: A female friend of mine seems extremely satisfied with her poly lifestyle. She has been poly for several years, with a break for monogamy that she regrets.

Neutral/negative experience: My partner has dated two people who would not describe themselves as being poly (they were monogamously interested in my partner). They knew that my relationship to my partner was primary, but still ended up with broken hearts when my partner broke up with them. My partner is fine. This doesn't look much different from the outcome I would expect if my partner had been monogamous.

Positive experience: I dated someone who knew both my primary partner and me. Doing so did not affect their friendship. I ended the relationship fairly amicably for reasons unrelated to non-monogamy.

Negative experience: A married couple who were living six hours apart opened up their marriage. When I met them they were not having any obvious issues with the arrangement. Eventually it came out that the husband was lying about partners both to his wife and to the other women. The rules of their relationship allowed him to have sex with other women as long as his wife knew about them, and yet he seemed compelled to lie whenever possible. The wife gains some comfort from the support of her lover, and has not yet decided whether to end the marriage.